This invention relates to a combination dust collector and heat exchanger.
Many boiler installations employ gravity separation dust collectors for removing entrained solid combustion products (hereinafter referred to as dust) from the boiler exhaust or flue gases prior to discharge to atmosphere. Gravity separation dust collectors are highly economical in such installations because they possess high cleaning efficiency with low draft loss -- thus making them adaptable to natural and forced draft systems -- and require little or no maintenance or cleaning.
Until recently, the operators of boiler installations of this type did not attempt to improve the overall thermal efficiency of the installation by extracting and reclaiming a portion of the available waste heat from the boiler exhaust gases because cheap fuel, such as wood, was in plentiful supply. Consequently, heat exchange apparatus such as economizers and air preheaters heretofore have been employed almost exclusively in large power plants, or in combination with cyclone, centrifugal or deflection dust collectors of the type disclosed in U.S. Pat. Nos. 1,795,909, 1,875,341, 2,060,169, 2,327,691, 2,437,294, 2,569,710 and 2,761,526. With sky-rocketing fuel prices, coupled with a decline in supplies of cheap fuel, however, the operators of such boiler installations are now searching for a method and apparatus for increasing thermal efficiency economically. One approach would be to install separate small-scale air preheaters or economizers generally similar to those previously used with large power plants; however, the capital investment involved in acquiring and installing these units typically is not warranted by the savings achieved by increased thermal efficiency because of the relatively small scale of the above-mentioned type of boiler installations.